This invention relates to a control system for peripheral devices which is suitable, for example, for use in an integrated circuit (IC) containing plural digital-to-analogue converters.
A system is proposed wherein two integrated circuits are connected with a bus line comprising two signal lines, a serial clock SCL line and a serial data DTA line, so that an integrated circuit supplies serial data to the other integrated circuit. Here, the integrated circuit which receives the serial data converts the serial data to various kinds of analogue control signals with digital-to-analogue converters being therein and supplies these converted analogue control signals to peripheral devices.
These analogue control signals are, for example, a contrast control signal, brightness control signal, and the like. These control signals are transferred on the two signal lines with serial data, therefore desired signal processes can be achieved without having input terminals corresponding to each control signal.
However, in order to test these integrated circuits to know whether the digital-to-analogue converters being therein can operate or not, or in order to make an evaluation to check if the linearity error of output signal of each digital-to-analogue converter is less than .+-.1/2 of the least significant bit in value, special troublesome testing is required during manufacturing. That is, the integrated circuit must have special terminals, just for testing, corresponding to each digital-to-analogue converter, for example terminals with testing holes through which a special fixture is set.